The present invention relates to monitoring a contaminated, dirty or inflammable condition caused by fallout dust. More specifically, the invention is directed to a new use of dust detection equipment to provide a warning for presence or an amount of dust or fine particles on a surface in an appliance.
A main purpose of an indicator for fallout dust is prevention of fire and explosions. However, one may envisage several important purposes, e.g. (a) being able to prevent particular odor related to dust/particle accumulations, (b) being able to improve efficiency of cooling units by preventing large accumulations of dust on cooling ribs, since such accumulations impair heat exchange capability, (c) general improvement/increasing efficiency of cleaning/service/maintenance programs, i.e. demonstrating more easily a need for cleaning, or (d) being able to maintain important parameters for electrical/electronic apparatuses within given tolerances.
In general it is previously known to measure dust and particle accumulations; however such measurements are typically made in industrial or research related environments. U.S. Pat. No. 4,793,710 discloses a method for measuring dust layers in coal mines, based upon an optical technique, and U.S. Pat. No. 5,412,221 also relates to an optical measuring method for small particle deposition (“fallout”) in connection with space research. U.S. Pat. No. 5,229,602 discloses an optical method for detecting contamination layers particularly on transparent surfaces (headlight glass, windshield) on vehicles.